IB predicted v final grades

I've been wondering how accurate that IB predicted grades are to exam grades, as someone who thought they would be predicted 4 points higher, I genuinely thought I deserved/ am at a higher score than was predicted. Is this common/ do you have personal experience? My school's average final grades are 35-37 and idk if my cohort is just a little worse this year but it doesn't seem like that's the current prediction and I'm getting the impression that my school might under predict students?

A similar thing happened with my school ☹️ They gave out much lower predicted grades to our cohort compared with previous years
In our school it had to do with change in the academic leadership team etc, so more like internal policy changes
But I still got offers from my top choice unis (even though I just about met the minimum grade requirements), so I wouldn't think it's the end of the world!

yeahh, i seriously think i'll do better on the final exams and it's really effing with my mind and i haven't been as motivated or focused (ironically)